The amazing Zerochromat 8 inch apochromatic refractor has been updated, with a theoretical Strehl ratio of 0.995. It is now available at only $4500 until 1st May. Details can be seen on our website at www.firefly85.com.
We are working on a new domain address, which will available soon.
A photo of this instrument is shown below, which comes complete with Moonlite motor-controlled focuser, 8 x 50mm finder, carbon composite tube, and is supplied in a birch ply flight case.

Attached Files

You might want to consider explicitly mention on the website that it's a folded refractor; the only place that piece of information is found is in the 'customer review' on http://www.firefly85...-refractor.html

Hi Thomas, the objective lens is a plano-convex singlet. The focal length is quite long, so the path is folded with two flat mirrors (high reflectivity), and after the rays cross over, all correction is done with a field lens and two small doublets. I have not stressed the use of fold mirrors on my web site, as people sometimes become confused with the Schupmann design, which is quite different, and very 'tweaky'. The Zerochromat design is very tolerant indeed, and the large fold flat can be adjusted to remove atmospheric refraction effects close to the horizon. Collimation is surprisingly simple, and much easier than a Newtonian. It stays collimated even when transported. I am sure that once there are lots of these instruments around, word will get out how good these are. I have already sold several of them.Peter

The only thing that I can guarantee about a theoretical Strehl ratio of 0.995 is that it will be slightly lower than this due to the inevitable optical and mechanical tolerances. However, it will be still be very high indeed, and more than good enough to satisfy the most experienced user. My own experience is that a bright star at 600x under good conditions yields a textbook perfect Airy disc and rings.

Hello, there are various reasons for no images yet - from the owner being on an oil platform in the North Sea to having moved house etc. Fear not! There will be images as soon as possible.We have several telescopes in the pipeline, with lots of interest from people with serious abilities in optical design, and who have verified the performance (and ordered a telescope).Watch this space!

The owner of a Zerochromat demonstration telescope will soon have a brand new telescope. So this demonstration telescope will soon be available, probably around the end of June, at only $3500, delivered to the US. The optics are perfect, so the performance is guaranteed.

The objective lenses and fold flats are made in-house, so we can guarantee the optical quality. For instance, the test plates for each side of the objective lenses have been made to better than 1/20 wave, so any departure from perfect can be easily picked up and corrected. The aim is for 1/8 wave or better for astigmatism. The power can be several fringes out, but we keep it to 3 fringes or less so that any departure from 1/8 wave of astigmatism can be clearly seen.This way, we can keep the Strehl ratio very high overall.

The owner of a Zerochromat demonstration telescope will soon have a brand new telescope. So this demonstration telescope will soon be available, probably around the end of June, at only $3500, delivered to the US. The optics are perfect, so the performance is guaranteed.

The objective lenses and fold flats are made in-house, so we can guarantee the optical quality. For instance, the test plates for each side of the objective lenses have been made to better than 1/20 wave, so any departure from perfect can be easily picked up and corrected. The aim is for 1/8 wave or better for astigmatism. The power can be several fringes out, but we keep it to 3 fringes or less so that any departure from 1/8 wave of astigmatism can be clearly seen.
This way, we can keep the Strehl ratio very high overall.

IMO, you need to get this demonstrator into the hands of someone who can "show it off" here in the states (I can do this since I'm newly retired from 37 years of government service). I could easily take this scope around to various observing locations to show how good it really is. I'm sure there are many who think that this scope is just too good to be true. An active demonstrator would ease the doubts I'm sure many have concerning this instrument (visual performance, keeping collimation, lateral color issues, etc.). Pictures of spot diagrams indicating theoretical performance and user reports looking at land based targets are nice but how does it really perform on the night sky?

If you are interested in "loaning" this scope out for end user testing and evaluation let me know. I would be happy to give a full write up concerning the scope.

Producer define his warranty, I think you can buy it without your doubts.

"IF NOT DELIGHTED WITH OUR ZEROCHROMAT 8 INCH REFRACTOR, THEN PLEASE RETURN IT WITHIN 60 DAYS FOR OUR 'NO QUIBBLE' GUARANTEE."

Interesting. If the company was here in the states, I could somewhat trust in the guarantee but if I ended up with a lemon (as I did with a maksutov optic set from Britain a few decades ago) what is the recourse if the company decides not to honor their guarantee? I had to suck on that lemon for a while

The thing might work as intended but I'm not sure this is what people want. It has two mirrors which may reduce light grasp and contrast. Not sure if that makes baffling more difficult as well. Also at f12 it goes against why people like Apo's. Wide well corrected fields for low power observing.

I think a telescope like this is very good way to have semi APO with a big diameter. The mirror can reduce a little bit light but not contrast. The Zerochromat has F12 ratio, but optical design is like F21 ratio.

I think a telescope like this is very good way to have semi APO with a big diameter. The mirror can reduce a little bit light but not contrast. The Zerochromat has F12 ratio, but optical design is like F21 ratio.

I like the design and have no roblem with the F/12 focal ratio since I'm a lunar/planetary observer. Everything about the scope looks promising. An 8" apo or simi apo would be a perfect telescope for the type of observing I do but as stated before, I have my doubts concerning it. Computer generated spot diagrams and a report using relatively low power observing of land based objects is no where near enough information to get me to lay out cash for a design that is still theoretical from the current information I can find about it. I have found no information revealing how this thing performs on the night sky.

I will test Zerochromat next month and I will make a review. Theoretical spot diagram looks very well, I compared Zerochromat, Oil Triplet and Achromat in a typical Photopic vision (490nm, 560nm, 620nm).

Still no serious observations. Jupiter misted out? Bummer. I can shoot a picture of the moon like that with a 60mm refractor. Full disk lunar shots don't reveall too much as far as high power instrument performance is concerned.

Hello all you doubters, this is a product that is very new to the market, and there are only a few examples in the UK. Our skies are notoriously poor for most of the time, so it will take a while to get proper images.We have some highly intelligent people on our side, who have the wit to be able to carefully examine the performance of this instrument. Physics works extremely well, and computer predictions of performance match the actual performace perfectly, as long as the optics are carefully made and mounted. This is my personal experience, and that of the select few who have been able to observe through these amazing instruments.We have been asked as to why we use carbon fibre tubes, instead of aluminium. The answer is quite simple: as the sagitta of the objective lens is small, the effect of a 40 degree C change in temperature is a 0.35mm change in focal length. At 1525mm tube length, an aluminium tube would change by 1.3mm over the same temperature range, which if multiplied by 3 gives an actual change of 3.9mm - quite intolerable! Carbon fibre has an approximate cte of 1/10 that of aluminium (depending on the way it is made), giving a change in length of precisely that of the objective lens. Naturally, there is the bonus of strength, plus light weight.